1. Technical Field
The present invention relates to a liquid ejecting head such as an ink jet recording head, and to a liquid ejecting apparatus provided with the liquid ejecting head. In particular, the invention relates to a liquid ejecting head provided with a wiring member that includes a wiring terminal corresponding to a pressure generating unit of the liquid ejecting head, and to a liquid ejecting apparatus.
2. Related Art
In regard to a type of liquid ejecting head, which discharges a liquid within a pressure chamber from a nozzle as droplets by subjecting the liquid to pressure fluctuation, there is a liquid ejecting head configured to eject droplets by deforming a piezoelectric element (a type of pressure generating unit) that is joined to a vibration plate. In this liquid ejecting head, the piezoelectric element is driven by applying a drive voltage (a drive pulse) thereto, thereby changing the volume of the pressure chamber, the liquid stored within the pressure chamber is subjected to pressure fluctuation, and droplets are ejected from the nozzle using the pressure fluctuation.
The piezoelectric element is electrically connected to a film-shaped wiring member (hereinafter referred to as a flexible cable), onto which an IC such as a Chip On Film (COF) or a Tape Career Package (TCP) that drives the piezoelectric element is mounted, and a drive voltage is supplied to the piezoelectric element via the flexible cable (for example, refer to JP-A-2011-167964). The piezoelectric element includes a lower electrode film, a piezoelectric layer and an upper electrode film. In general, one of the electrodes (for example, the lower electrode film) is an element-shared electrode, which is shared by a plurality of the piezoelectric elements, and the other electrode (for example, the upper electrode film) is formed from individual element electrodes, which are patterned individually for each of the piezoelectric elements. The piezoelectric layer, which is interposed between the element-shared electrode and the individual element electrode, is a piezo-active portion in which piezoelectric deformation occurs due to the application of a drive voltage between the two electrodes.
The flexible cable described above is configured such that, for example, a control IC, which controls the application of the drive voltage to the piezoelectric element, is mounted on the surface of a base film such as a polyimide. In addition, a wiring pattern and a wiring terminal are formed on the flexible cable, and an insulating solder resist covers the wiring pattern, the control IC and the like except for the wiring terminals provided on both end portions of the flexible cable.
The piezoelectric element described above is accommodated by a member formed from a silicon single crystal substrate referred to as a protective substrate (and alternatively, is also referred to as a sealing plate). The terminal portions of the piezoelectric element are disposed within a wiring vacant portion that is provided in the protective substrate. Furthermore, a first end portion of the flexible cable is inserted through the wiring vacant portion, and the wiring terminal formed on the first end portion is electrically connected to the terminal corresponding to the piezoelectric element.
However, in this type of liquid ejecting head, in order to accommodate the demand for miniaturization, the miniaturization of all the members that configure the liquid ejecting head is also being devised. In regard to the protective substrate described above, which is one of the components, together with the miniaturization, where the flexible cable is inserted through the wiring vacant portion, the wiring vacant portion is a space narrow enough that it is possible to insert the first end portion of the flexible cable therethrough. Furthermore, together with the increase in the number of nozzles and the increase in density, the respective terminals configuring the terminal portion are also arranged at a high density and the interval between the terminals is narrow. Therefore, when the wiring work is performed, it is necessary to precisely join the wiring terminals with the terminals of the piezoelectric elements within a narrow space. In such a case, in a typical flexible cable, the thickness of the solder resist that covers the portions except for the terminals becomes a problem. In other words, the thickness of the solder resist is approximately 0.2 mm, for example. However, when the wiring work is performed in the narrow wiring vacant portion described above, there is a concern that the solder resist will make contact with a member (the protective substrate) that forms the wiring vacant portion by partitioning and that the joining positions of the respective terminals will shift.
In addition, in general, there is variation in the coating range of the solder resist of the flexible cable, and when a portion that is not covered by the solder resist makes contact with the protective substrate, which is formed from a silicon single crystal substrate, there is a concern that this will cause short circuiting due to the protective substrate being conductive.